December 2, 2013

All Terrain Scooter Redux

The original version of my all-terrain electric scooter suffered from a number of problems, the most important of which was in the motors I used. The triple CIM motors were just not capable of providing both the top speed and acceleration I wanted out of the vehicle. Actually they could, but just not for very long before the insulation on their windings turned into a melty black mess.

After some attempted snow-scootering during the northeast snowstorm last year, I decided I was sick of the freshly roasted motor smell, and stored away the scooter until the summer. A full teardown of the scooter revealed enough unnoticed or impending failures that I decided to scrap pretty much the entire mechanical end of the original scooter.

Version 2 features the same HobbyKing LiPo battery pack and Kelly 72V 200A brushed motor controller as the original, but nearly everything else is new. Replacing the CIMs are a pair of Magmotor S28-200's, which are slightly larger than the S28-150's of battlebot fame. Like before, the motors are mechanically coupled to one output shaft through a gearbox reduction, and connected electrically in series.

This version also has even bigger wheels (because the old ones clearly weren't large enough...), and over a foot of clearance everywhere.

"Lefty" type leading link fork, for no better reason than that I like how they look:

This version of the scooter also fixes the chain and chain tensioner problems of the previous version. A pair of connected sprockets at the pivot of the rear swingarm ensure that chain length remains constant over the travel of the suspension. This way, I don't need to use any sort of chain tensioner.

The shock absorber on the rear swingarm is a very fancy downhill mountain bike part. It is extremely adjustable, and damping in compression and extension directions are independently adjustable.

Here are the dual magmotor S28-200's. Right, now the Kelly controller is limited to 100A at 60V, meaning that each motor gets 100A at 30V. This works out to an acceleration of .54 g (at half the controller's current limit...). This acceleration is only actually reachable if you lean way over the handlebars. As I have experienced, you are simply thrown off if you throttle hard without doing this.